This invention relates to advanced epoxide resins which polymerise on exposure to actinic radiation, to methods of preparing them and of polymerising such resins by means of actinic radiation, to supports bearing thereon such a resin in the polymerisable state, and to supports bearing thereon a resin polymerised by means of actinic radiation.
Substances capable of becoming polymerised on exposure to actinic radiation are used in, for example, the preparation of printing plates for offset printing and of printed circuits, and for coating metals, such as in the manufacture of cans (see e.g., Kosar, "Light-sensitive Systems: Chemistry and Applications of non silver halide photographic Processes", Wiley, New York, 1965, 473 pp.; Delzenne, "Synthesis and Photocrosslinking of light-sensitive Polymers" in European Polym. J., Suppl., 1969, pp. 55-91; William, "Photopolymerisation and Photocrosslinking of Polymers" in Fortschr. chem. Forsch., Vol. 13 (2), 227-250). There are various drawbacks in the substances presently available which may be polymerised by exposure to actinic radiation. Some are so unstable that they must be applied to substrate only immediately prior to exposing them to actinic radiation. Others are relatively insensitive and need lengthy exposure to actinic radiation in order to become sufficiently polymerised. Others, after being polymerised, are not resistant to etching baths used in subsequent processes.
In most cases the reproduction of an image is desired: a layer of the polymerisable material is exposed to actinic radiation imagewise as through a negative and then "developed" by being washed with a suitable liquid, such as perchloroethylene, methylene chloride, ethylene dichloride, acetone, ethyl methyl ketone, cyclohexanone, n-propanol, ethanol, toluene, benzene, ethyl acetate, and mixtures thereof, to dissolve and remove that portion of the layer which was not polymerised by exposure to actinic radiation.
However, the use of such organic solvents to develop the image is often undesirable, on grounds of their flammability or toxicity, and so the need exists for substances which may be polymerised by means of actinic radiation and then developed by aqueous media.
It has now been found that, by using certain novel advanced epoxide resins, the aforesaid disadvantages of materials previously available for polymerisation by actinic radiation can be at least substantially overcome.
The use of photopolymerisable advanced epoxide resins has previously been described in British Pat. No. 1090142, but the only resins mentioned are derivatives of 2,2-bis(4-hydroxyphenyl)propane. We found such resins to be not water-soluble, and there is no indication in that Specification that, by the use of certain non-aromatic advanced epoxide resins, it is possible to obtain water-developable photopolymerisable products.
Advanced epoxide resins in which the free hydroxyl groups have been treated with unsaturated acid and alcohol derivatives have also been described in West German Offenlegungsschrift No. 2300542. Again, only resins derived from phenols are described, and we have found them not to be water-soluble. The properties of these materials after irradiation are not described.